Driver Assistance System

ABSTRACT

The invention relates to a driver assistance system for a motor vehicle, comprising a speed detection device ( 22 ) for detecting driving data in the form of a speed (v k ) of the motor vehicle ( 10 ), a preceding vehicle detection device ( 14 ), which comprises as a first component at least one video camera ( 18 ) and as a second component at least one distance sensor ( 20 ), for detecting driving data in the form of a distance (A) from a preceding vehicle ( 16 ) driving in front of the motor vehicle ( 10 ), a preceding vehicle speed determination device for determining driving data in the form of a preceding vehicle speed (v Vf ) of the preceding vehicle ( 16 ), and an electric control unit ( 28 ), which is equipped to trigger an autonomous deceleration of the motor vehicle ( 10 ) with the presence of predetermined brake trigger driving data and to terminate the autonomous deceleration of the motor vehicle ( 10 ) with the presence of predetermined brake abortion driving data. According to the invention, the electric control unit ( 28 ) is equipped to carry out a method comprising the following steps: redundant detection of preceding vehicle driving data (A, v Vf ) of the preceding vehicle ( 15 ), and non-redundant detection of the preceding vehicle driving data (A, v Vf ) if a redundant detection of the preceding vehicle driving data (A, v Vf ) is not possible, comparing the non-redundantly detected preceding vehicle driving data to preceding vehicle driving data redundantly detected within a predetermined time (t), and using the non-redundantly detected preceding vehicle driving data in order to carry out step (d) if the non-redundantly detected preceding vehicle driving data correspond to the redundantly detected preceding vehicle driving data.

The invention generally relates to a driver assistance system for a motor vehicle, that, according to various embodiments, has (a) a speed detection device for detecting driving data in the form of a speed of the motor vehicle, (b) a preceding vehicle detection device, which comprises at least one video camera as a first component and at least one distance sensor as a second component, for detecting driving data in the form of a distance from a preceding vehicle driving in front of the motor vehicle, (c) a preceding vehicle speed determination device for determining a preceding vehicle speed of the preceding vehicle and (d) an electric actuation unit which is configured to trigger autonomous braking of the motor vehicle when predetermined brake trigger driving data are present, and to terminate autonomous braking of the motor vehicle when predetermined brake abort driving data are present.

Driver assistance systems of the general type under consideration are known and serve to reduce the severity of an accident or entirely avoid an accident through autonomous braking of a motor vehicle, which can also be referred to as partial braking, just before an anticipated collision of the motor vehicle with the preceding vehicle. A preceding vehicle detection device is known for generating the necessary signals for triggering the autonomous braking.

A disadvantage with known driver assistance systems is that the autonomous braking is aborted if the preceding vehicle detection device no longer detects a preceding vehicle. It has become apparent that such driver assistance systems frequently terminate the autonomous braking too early, with the result that the risk of collision and the potential intensity of the accident increase.

It is an object of the invention to overcome disadvantages in the prior art by means of an improved driver assistance system in which, according to various embodiments of the present invention, the electric actuation unit is configured to carry out a method having the steps of (i) redundant detection of preceding vehicle driving data of the preceding vehicle and (ii) if at least one of the component fails so that redundant detection of the preceding vehicle driving data becomes impossible, (aa) non-redundant detection of the preceding vehicle driving data, (bb) comparison of the non-redundantly detected preceding vehicle driving data with preceding vehicle driving data which are detected redundantly within a predefined time, and (cc) if the non-redundantly detected preceding vehicle driving data correspond to the redundantly detected preceding vehicle driving data, use of the non-redundantly detected preceding vehicle driving data to check for the presence of brake trigger driving data and/or brake abort driving data.

An advantage of the claimed invention is that the driver assistance system can reliably bring the motor vehicle to a standstill even if, for example, the video camera can no longer detect the preceding vehicle because the motor vehicle is rolling and pitching too strongly and as a result redundant detection of preceding vehicle driving data fails.

Within the scope of the following description, a speed detection device is understood to be, in particular, a tachometer or tachograph. The speed detection device can alternatively or additively also be formed by a device of a brake system of the motor vehicle which determines the speed from wheel speeds.

A preceding vehicle detection device is understood, in particular, to be any sensor which is designed and provided for detecting a relevant preceding vehicle of the motor vehicle, that is to say to identify this as a preceding vehicle or detect data therefrom, such as for example the distance from the motor vehicle.

Brake trigger driving data are understood, in particular, to be data which describe movement states of the motor vehicle in absolute or relative terms with respect to the preceding vehicle and in the presence of which autonomous braking is to be carried out. For example, driving data then therefore become brake trigger driving data if they are beyond a predetermined limiting value. If, for example, the continuously measured driving data item of the distance drops below a minimum distance so that autonomous braking is to be initiated, the corresponding distance becomes a brake trigger driving data item.

Brake abort driving data are understood, in particular, to be data in whose presence the autonomous braking is to be aborted.

Preceding vehicle driving data are understood, in particular, to be data which describe a movement state of the preceding vehicle in absolute or relative terms with respect to the motor vehicle. This may also include a preceding vehicle ID or the relative speed from the motor vehicle. The preceding vehicle driving data are also driving data.

The condition that the non-redundantly detected preceding vehicle driving data correspond to the redundantly detected preceding vehicle driving data is to be understood to mean, in particular, that the respective data differ from one another only by a predefined relative or absolute deviation.

The preceding vehicle detection device is preferably designed to detect relevant preceding vehicles. A relevant preceding vehicle is a preceding vehicle which is in the movement path of the motor vehicle.

An electric actuation unit is understood to be, in particular, any computing unit which performs open-loop control on the assemblies of the motor vehicle or closed-loop control of a process. It is possible here, but not necessary, for the electric actuation unit to be composed of a plurality of sub-units. It is therefore possible, for example, for all the driving data sensors referred to below or other sensors to have joined to them an evaluation unit which pre-processes measurement data and transmits it in encoded form to a main actuation unit.

It is also possible for the preceding vehicle detection device and preceding vehicle speed detection device to be combined in a single device. For the present invention it is irrelevant how individual functionalities are divided up among assigned devices. It is therefore possible for the preceding vehicle detection device to determine so many data items that the preceding vehicle speed of the preceding vehicle can be determined therefrom. In this case, the preceding vehicle speed determination device is part of the preceding vehicle detection device.

For example, the preceding vehicle detection device can be configured to determine the distance of the motor vehicle from the preceding vehicle at regular time intervals, and to calculate a relative speed from the preceding vehicle from the change in the distance data over time. The preceding vehicle speed is therefore obtained as a vector sum from the speed and a relative speed between the motor vehicle and the preceding vehicle. In this case, the preceding vehicle speed determination device is part of the preceding vehicle detection device.

Redundant detection of the preceding vehicle driving data is understood to mean, in particular, that at least two components of the preceding vehicle detection device detect the preceding vehicle simultaneously, and that the preceding vehicle is detected. Failure of a component is understood to be, in particular, any event which leads to the component no longer supplying usable signals. This may be due, for example, to the component being destroyed or the motor vehicle rolling or pitching so strongly that the data obtained can no longer be evaluated.

A distance sensor is understood to be any device which is designed and arranged to determine a distance from a preceding vehicle. For example, the distance sensor comprises a laser sensor and/or a radar sensor.

In this case, for example the distance sensor can also supply distance data, but the video camera has failed so that it is not ensured that the distance data relate to the preceding vehicle. In this case, the distance data which are detected by the distance sensor are not redundant.

The comparison of non-redundantly detected preceding vehicle driving data with preceding vehicle driving data which are detected redundantly within a predefined time is understood to mean, in particular, that a deviation between the two preceding vehicle driving data items is determined and compared with a predefined threshold value. If the two preceding vehicle driving data items deviate by, for example, less than 5% from one another, it is assumed that the distance sensor is still measuring the distance from the preceding vehicle and not, for example, the distance from another object. The predefined time may be, for example, less than a second. The preceding vehicle ID and the relative speed can also be used to assess whether the redundant detection of the preceding vehicle driving data has become impossible. It is therefore possible to provide that a the redundant detection is considered to be possible if the preceding vehicle ID (identification number) of the detected object remains the same.

In one embodiment, the electric actuation unit is designed to carry out a method which, when at least one of the components fails so that redundant detection of the preceding vehicle driving data becomes impossible but non-redundant detection is possible, carries out the additional steps of determining whether a last-detected distance of the preceding vehicle from the motor vehicle undershoots a predefined minimum distance, and if this is the case of suppressing an abort of the autonomous braking. Premature aborting of the autonomous braking is therefore avoided.

In other words, in situations in which redundant detection is not possible and there is already a high probability of the motor vehicle already being in a state of autonomous braking because the minimum distance from the preceding vehicle has been undershot, the autonomous braking continuous to be maintained. This prevents aborting of the autonomous braking simply because driving data are absent being able to constitute a safety risk.

The predefined minimum distance is basically freely selectable. However, it has become apparent that distances below 3 m, in particular of less than 2 m, are well suited.

In another embodiment, the electric actuation unit is designed to carry out a method having the additional steps: if all the components of the preceding vehicle detection device fail after the redundant detection of the preceding vehicle, (i) extrapolation of the distance from the preceding vehicle and the preceding vehicle speed, and (ii) use of the extrapolated distance and/or of the extrapolated preceding vehicle speed as driving data for checking whether the predetermined brake trigger driving data and/or brake abort driving data are present. The distance and the preceding vehicle speed are extrapolated, in particular, from earlier measurement data which has been stored in a digital memory of the actuation unit.

In other words, the distance and the preceding vehicle speed are then used for the checking as to whether the predetermined brake trigger driving data and/or brake abort driving data are present if, and only if, no other better (namely redundant) measurement data are present. As a result, a situation may arise in which the autonomous braking is not aborted even though it could be aborted, which would intrude on the driver's autonomy without reason. However, this disadvantage is more than made up for by the advantage that the autonomous braking is not aborted because only corresponding driving data are missing even though this gives rise to a greater severity of accident or even actually brings about an accident.

The electric actuation unit is preferably embodied in such a way that it suppresses the aborting of the autonomous braking until the motor vehicles comes to a standstill. Alternatively or additively, the suppression of the aborting of the autonomous braking ends when the preceding vehicle is detected redundantly and the driving data correspond to the brake abort driving data.

A motor vehicle having a driver assistance system according to the inventive embodiments is also contemplated. The motor vehicle may be, for example, a utility vehicle.

The invention will be explained in more detail below using an exemplary embodiment and with reference to the appended drawing, in which:

FIG. 1 shows a schematic view of a motor vehicle according to the invention with a driver assistance system according to the invention.

FIG. 1 shows a motor vehicle 10 which has a front side 12 on which a preceding vehicle detection device 14 is arranged. The preceding vehicle detection device 14 is designed to detect a preceding vehicle 16 and has a first component in the form of a video camera 18 with a field of vision G and a second component in the form of a distance sensor 20. The distance sensor 20 is designed to measure a distance A between the front side 12 of the motor vehicle 10 and a rear side of the preceding vehicle 16.

The motor vehicle 10 also has a speed detection device 22 in the form of a tachometer, a yaw rate sensor 24 and a deceleration sensor 26. The preceding vehicle detection device 14, the speed detection device 22, the yaw rate sensor 24 and the deceleration sensor 26 are driving data sensors which detect driving data of the motor vehicle 10. These are all connected to an electric actuation unit 28 by means of cables. The electric actuation unit 28 comprises a digital memory 30 in which measurement data which are detected by the driving data sensors can be stored in a buffered fashion.

The distance sensor 20 functions, together with the speed detection device 22 and the electric actuation unit 28, as a preceding vehicle speed determination device for determining a preceding vehicle speed v_(vf). In order to determine the preceding vehicle speed v_(vf), the distance sensor 20 measures the distance A at a time interval of, for example, 100 m/s and calculates therefrom a relative speed v_(relative) between the motor vehicle 10 and the preceding vehicle 16. The relative speed v_(relative) is added to a speed v_(K) of the motor vehicle 10, so that the preceding vehicle speed v_(vf) is obtained.

A method which continuously detects the distance values A from the distance sensor 20 runs on the electric actuation unit. At the same time, image data are obtained from the video camera 18 and are examined by means of image recognition to determine whether a preceding vehicle 16 is present. If this is the case, a preceding vehicle ID is assigned to the preceding vehicle 16. At the same time, the respective distance A and the respective preceding vehicle speed v_(vf) are linked to the preceding vehicle ID. The preceding vehicle ID, the distance and the preceding vehicle speed v_(vf) are preceding vehicle data and also constitute driving data.

The electric actuation unit 28 compares incoming data with brake trigger driving data stored in the digital memory 30. If sufficiently large correspondences are found, the electric actuation unit 28 triggers autonomous braking of the motor vehicle 10 by sending an electric brake signal to brakes 32.1, 32.2, 32.3, 32.4 via a bus line (not indicated), after which the brakes 32 brake the motor vehicle 10.

As long as the video camera 18 and the distance sensor detect the preceding vehicle 16 as a preceding vehicle which is driving in front of the motor vehicle 10, redundant detection of the preceding vehicle 16 occurs. That is, it can be assumed that the distance A is actually a distance from a preceding vehicle and not, for example, a distance from another object in front of the motor vehicle 10, for example a crash barrier. During the autonomous braking a situation may arise in which the video camera 18 can no longer detect the preceding vehicle 16, for example because the relative movement between the motor vehicle 10 and the preceding vehicle 16 is so large that the image evaluation no longer succeeds in a stable fashion. In this case, the video camera 18 fails as a first component of the preceding vehicle detection device 14, but on the other hand the distance sensor 20 continues to supply distance data. In this case, the electric actuation unit 28 determines whether a distance A_(redundant) which was detected redundantly last is smaller than a predefined minimum distance A_(min) of, for example, 2 m. If this is not the case, the distance A_(redundant) which was detected last both by the video camera 18 and by the distance sensor 20 was therefore smaller than the minimum distance A_(min) and an abort of the autonomous braking located in the profile is suppressed until either the motor vehicle 10 comes to a standstill or until a redundantly detected distance is determined again.

It is possible to accommodate a situation where autonomous braking is carried out and the video camera 14 can no longer detect the preceding vehicle 16, for example because the preceding vehicle 16 has approached the motor vehicle 10 so closely that detection is no longer possible. This can lead, for example, to a situation in which on the basis of the data from the video camera 18 a further preceding vehicle ID is generated so that the impression is given that two objects are present even though they are both the preceding vehicle 16. In this case, a preceding object is detected by the distance sensor 20 and the electric actuation unit 28 assigns a preceding object ID to these data items. It is then continuously determined whether these preceding object data items correspond to the preceding vehicle data. This is to be understood as meaning that the preceding object data which cannot be reliably assigned to a real object are compared with those redundantly detected preceding vehicle data items which have been detected previously. If a sufficiently high degree of similarity is detected, the preceding object data are used as driving data for checking whether the predetermined brake abort driving data are present. In other words, it is assumed that the preceding object which is detected by the distance sensor 20 continues to be the preceding vehicle 16. The driving data which are determined for this object are then used for the comparison with the predetermined brake abort driving data.

If the electric actuation unit 28 does not receive from the video camera 18 and the distance sensor 20 any data which permit determination of the distance A, the actuation unit 28 extrapolates the distance A and the preceding vehicle speed v_(vf) by means of the data measured last. The driving data which are extrapolated in this way are then compared with the predetermined brake abort driving data and the autonomous braking is aborted, if appropriate. 

1. A driver assistance system for a motor vehicle, having (a) a speed detection device (22) for detecting driving data in the form of a speed (v_(K)) of the motor vehicle (10), (b) a preceding vehicle detection device (14), which comprises at least one video camera (18) as a first component and at least one distance sensor (20) as a second component, for detecting driving data in the form of a distance (A) from a preceding vehicle (16) driving in front of the motor vehicle (10), (c) a preceding vehicle speed determination device for determining driving data in the form of a preceding vehicle speed (v_(vf)) of the preceding vehicle (16) and (d) an electric actuation unit (28) which is configured to trigger autonomous braking of the motor vehicle (10) when predetermined brake trigger driving data are present, and to terminate autonomous braking of the motor vehicle (10) when predetermined brake abort driving data are present, characterized in that (e) the electric actuation unit (28) is configured to carry out a method having the steps (i) redundant detection of preceding vehicle driving data (A, v_(vf)) of the preceding vehicle (15), and (ii) if redundant detection of the preceding vehicle driving data (A, v_(vf)) is impossible, non-redundant detection of the preceding vehicle driving data (A, v_(vf)) comparison of the non-redundantly detected preceding vehicle driving data with preceding vehicle driving data which are detected redundantly within a predefined time (t), and if the non-redundantly detected preceding vehicle driving data correspond to the redundantly detected preceding vehicle driving data, use of the non-redundantly detected preceding vehicle driving data in order to carry out step (d).
 2. The driver assistance system as claimed in claim 1, characterized in that the electric actuation unit (28) is designed to carry out a method having the additional steps: if at least one of the components (18, 20) fails so that redundant detection of the preceding vehicle driving data (A, v_(vf)) becomes impossible, (i) determination whether a last-detected distance (A) of the preceding vehicle (16) from the motor vehicle (10) undershoots a predefined mean distance (A_(min)), and (ii) if this is the case, suppression of an abort of the autonomous braking.
 3. The driver assistance system as claimed in one of the preceding claims, characterized in that the electric actuation unit is designed to carry out a method having the additional steps: if all the components (18, 20) of the preceding vehicle detection device (14) fail after the redundant detection of the preceding vehicle, extrapolation of the distance (A) from the preceding vehicle (16) and of the preceding vehicle speed (v_(vf)), and use of the extrapolated distance (A) and/or of the extrapolated preceding vehicle speed (v_(vf)) in order to carry out step (d).
 4. The driver assistance system as claimed in one of the preceding claims, characterized in that the electric actuation unit is designed to detect whether at least one of the components of the preceding vehicle detection device has failed by detecting whether the video camera (18) outputs signals and does not detect a preceding vehicle (16).
 5. A motor vehicle having a driver assistance system as claimed in one of the preceding claims. 